The striking staff are members of the Unite and RMT unions, whose members voted overwhelmingly in favour of strike action.

A second 48-hour walkout began at 6:30 am today after fresh talks ended in stalemate.

The striking workers claim cuts to pay and benefits and a move from a two-week to three-week working cycle add up to an overall pay cut of around 30 per cent for some contractors, a claim refuted by Wood Group.